The environmental pollution may be defined as direct or indirect undesirable changes in our surrounding as a
result of human activities that have harmful effects on plants, animals and human beings.
A substance, which causes pollution, is known as pollutant. Pollutants may be solid, liquid or gaseous substance
present in greater concentration than in natural abundance and are produced due to human activities or due to
natural happenings
It is a protective blanket of gases which is surrounding the earth. The atmosphere is
held to the earth by the force of gravity. The total mass of atmosphere is about 5 × 1015
metric tones. The constituents which make up the atmosphere are gases, water vapours
and arosols
It occurs due to the presence of undesirable solids or gaseous particles in the air.
Gaseous air pollutants
It has been found that about 75% of solar energy reaching the earth is absorbed by the earth’s surface and,in
turn, this increases the temperature of the earth
The pH of rain water is 5.6 due to the presence of H+ ions formed by the reaction of rain water with carbon dioxide
present in the atmosphere as per following reactions
Word smog is obtained from the combination of the words smoke and fog. It is the one of the most common
examples of air pollution that occurs in many cities through out the world. There are two types of smog as
explained below
Components of photochemical smog, NO and O3, irritate the nose and throat and their high
concentration causes headache, chest pain, dryness of the throat, cough and difficulty in
breathing
Stratospheric Pollution :
Formation and Break down of Ozone
In Antarctica, scientists working reported about the depletion of ozone
layer commonly known as ozone hole over the south pole
In summer season, nitrogen dioxide and methane react with chlorine monoxide and chlorine atom forming
chlorine sinks and, thereby, preventing much ozone depletion.
UV radiation lead to ageing of skin, cataract, sunburn, skin cancer, killing of many phytoplanktons,
damage to fish productivity etc
Pollution of water originates from human activities
Pathogens :(Infection or disease causing agents) Water pollutants which are the disease
causing agents are called pathogens. Pathogens include bacteria and other organism that enter
water from domestic sewage and animal excreta
Bacteria present in large population causes the decomposition of organic matter present in water.
They consume oxygen dissolved in water.
The amount of oxygen required by bacteria to break down the organic waste present in a certain
volume of a sample of water is called biochemical oxygen demand (BOD).
Chemical pollutants include water soluble such as cadmium, mercury, nickel etc. All these metals
are dangerous to human because our body can not excrete them. Over the time, the concentration of
these metals crosses the tolerance limit and thus, these metals then can damage kidneys, central
nervous system liver, etc.
Eutrophication
Eutrophication
Fluoride : Drinking water should contain fluoride ions concentration up to 1 ppm or 1 mg dm–3. Its
deficiency in drinking water causes diseases such as tooth decay etc
Insecticides, pesticides and herbicides cause soil pollution.
Generated by cotton mills, food processing units, paper mills and textile factories.
Green chemistry is a way of thinking and is about utilising the existing knowledge and principles of chemistry
and other services to reduce the adverse impact on environment
